When a tooth is affected by deep decay, it is sometimes necessary to devitalize the tooth. To this end, it is necessary to remove infected tissues from the tooth and from the root of the tooth and shape a canal that is to be filled by a material constituted by gutta-percha or other canal filler pastes.
Endodontic instruments are used to perform these operations. These instruments can be likened to small-diameter drills which are used to ream and/or cut out the dentine from the root of the tooth to shape the canal that has to receive the gutta-percha or other canal filling pastes.
This treatment is therefore done in a mechanized way and the endodontic instruments are planned, at the time of their design, to have a hardness sufficient to go through the dentine which is a semi-hard material, while at the same time having a certain degree of flexibility to be able to take the internal shape of the root of the tooth. To this end, the endodontic instruments proposed for several years now have been made out of a nickel-titanium alloy instead of steel wire.
Present-day endodontic instruments are generally manufactured from a cylindrical rod on which one or more helical cuts are made, conventionally by means of a milling method. The cutting surfaces generate a cutting edge at their intersection.
With the classic means of grinding or milling, the cutting operations performed result from the combining of simultaneous motions of rotation and a forward movement of the wire (the part to be machined) before the grinder or the cutter. The instruments thus machined have a known geometry (circle, square, polygon, etc) in their section perpendicular to the axis of the wire, predetermined by the machining cycle. The centers of all these cross-sections together define the load-bearing core of the cutting edge along the cutting portion of the instrument. The result of the use of classic machining means (grinding or milling) is that this load-bearing core extends rectilinearly and coincidentally with the axis of the wire constituting the initial part to be machined.
The instruments used at present require great vigilance and precise dexterity on the part of the practitioner. Indeed, two mutually contrary phenomena can arise with known endodontic instruments:                either the edge of the endodontic instrument slips on the material of the dentine;        or the edge of the endodontic instrument gets engaged far too rapidly in the material of the dentine, leading to the phenomenon of overtight screwing, at the end of which the instrument gets jammed in the material.        
In both cases, the machining of the canal is not done accurately or even is not done at all.
It must be noted that when the endodontic instrument gets jammed in the material, it frequently happens that the instrument breaks. Now the breaking of the endodontic instrument inside the canal results in major excess cost of operation for the practitioner and a risk to the patient's health.
Besides, it is classic to use fluid during the reaming of a canal, and this fluid should possibly be a lubricant liquid or an antiseptic solution.
However, presently used-day instruments considerably limit the effect of these fluids. Indeed, when reaming a tooth canal, the diameter of the canal is that of the instrument used and therefore the space between the wall of the canal and the rotating instrument does not enable the flow of a fluid. In certain cases, the shape of the flutes of the active part of the instrument even tends to drive the fluid out of the canal.
In any case, the effect of the fluid proves to be very limited in practice.
It is therefore necessary for the practitioner to carry out the reaming and irrigating operations separately, in interposed them, and this slows down the work.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.